The present invention relates, in general, to photoelectric cells, and in particular to a new and useful photoelectrochemical cell of the type which has an efficiency of about 10%, but utilizing as a semiconductor material a ternary compound of the material system CuInSe.sub.2 or CuInS.sub.2, which acts as the working electrode, and an iodine-iodide solution.
Photoelectrochemical solar cells have an advantage over photovoltaic systems in that providing a contacting connection is much simpler. The transition from solid to liquid raises no problems for the electric connection, nor does it lead to undesirable mechanical stresses between materials having different crystal structures. What is troublesome, however, is the photocorrosion of the semiconductor. This is a process which is concurrent with the regenerative operation of the cell and one which unfavorably affects the stability of the photoelectrochemical solar cell.
In prior art photoelectrochemical solar cells systems having an efficiency of about 10% and intended to convert solar energy inexpensively, the starting material of the semiconductor is frequently expensive. In addition, mostly electrolyte solutions are employed which are toxic, and the cells must be hermetically enclosed to prevent the solution from decomposition. As to disclosure of such systems, see for example: "Enhanced Photoelectrochemical Solar-Energy Conversion by Gallium Arsenide Surface Modification" by Parkinson et al which shows n-GaAs in an aqueous selenide-polyselenide solution (Appl. Phys. Lett. 33(6), Sept. 15, 1978, p. 521); "Design of a 13% Efficient . . . Cell" by Gronet et al, that shows n-GaAs.sub.l-x P.sub.x in an organic electrolyte (Nature, Vol. 300, Dec. 23 and 30, 1982, p. 733); and "An Efficient Photocathode for . . . Cells" by Miller et al which shows p-InP in a strongly acid solution of vanadium-hydrochloric acid (Journal of the American Chemical Soc., Vol. 102 p. 6555, (1980)).
Recent developments in semiconductor materials having small absorption lengths for the solar spectrum radiation may be learned from: J. Electrochem. Soc., March 1983, Reviews and News Nos. 235 to 237, pages 87C-88C. Attention is drawn to CuInSe.sub.2 in this publication, and a wide range of possible applications which is indicated in No. 237, including photovoltaic systems of CuInSe.sub.2 /CdS for solar cells.